Upgrading a 1970 911t

[dpetteng]

So I just purchased a 1970 911t with matching numbers engine. From looking at the "t" versus the "E' and "S" versions, what is the fundamental differences between these engines and can they therefore, be upgraded?

I am guessing that the key differences are compression ratio, cam etc. Anything else?

Dave

[Trackrash]

T's had non counterweighted cranks, cast iron cylinders, and mild cams.

You should buy Wayne's "How to rebuild 911 motors" and Bruce Anderson's "Porsche 911 Performance Handbook". They have all the details.

Read my garage for my motor's mods.

[dpetteng]

So I read the book and it doesn't really touch on what you can do to upgrade form a "t" spec to an "e" or "s" spec.

Is it just a case of new barrels, pistons and cam?

[bgyglfr]

P&Cs and cams will get you close to an E I've done it and it's a nice upgrade. S Pistons with E cams make a fun motor. The counterweighted crank is a non issue unless you spend a lot of time at 8k rpm. Actually, many will argue that you crank will spin up faster because it's lighter. The only difference that can be expensive is porting the heads which again isn't necessary unless you plan on building a high rpm motor.

[dpetteng]

Fantastic, so any idea where I can get "S" P&C's and "e" cams?

[bgyglfr]

What are your T cylinders like? You can reuse them and just buy some JE pistons. If the cylinders are bad just get 85mm pistons and have your cylinders bored to match. Your cams can be re ground to E or you can source a set. Pm me if you want. I will send you my number.

[speedo]

They are high compression compared to the 2.4 gear. Best bang for the buck is to stroke the engine to 2.4 by swapping out the crank and rods. A 2.2 T engine will basically become a 2.4 E engine. I kept the T cams as E cams didn't give me comfortable valve clearance. The books talk about the benefit of the 2.2 T-E-S pistons. Bumping the 2.2 S pistons into a 2.4 with a 70.4 crank and rods is the real deal...but the 2.2 T in a 2.4 configuration is pretty sweet too.
Just say'in...

Speedo

[bgyglfr]

Speedo,
Good point. That would be a good option as long as you are splitting the case. Nice torquey street motor. The OP just asked for upgrade options. I assumed he wasn't planning a full rebuild.

Dave,
Are you planning a rebuild or just want some more pep out of your motor? Top end upgrade can be done for $1500-$2000. A full rebuild can be 4 times that. Especially if the case needs work.

[safe]

Don't forget that you need to re-jet the carbs. Unless you really want a E or S clone and get the correct MFI (mega bucks these days).

[dpetteng]

So I am going to have it torn down anyhow but its a matching numbers car so I don't want to bastardize it too far. To be honest I want more than 125hp in an engine that has some sense of being original, make sense?

[safe]

S P&C, E-cam and modified carbs. It will be a sweet street engine and I don't think anyone (future buyer) will mind or even notice if you don't say anything.

[dpetteng]

So I am stuck between a set of "e" NOS barrels and Pistons I have found and having my Cast Iron cylinders bored to 85mm and have JE Pistons.

I can see that "e" P&C's come out at 9.1:1 compression and JE's are 9.5:1.

As I am going to using this in the UK where higher rated petrol is available, should I go for the JE's as detonation is less of a problem?

Dave

[bgyglfr]

9:5-1 shouldn't be an issue on quality pump gas. If cost is the same, I would go with the NOS P&Cs. Just read a thread on JEs with cast pistons that you might want to take a look at before making your decision. A third option is to give supertec a call. They have several options of P&Cs available.

JE pistons with cast iron barrels?

[Trackrash]

A friend of mine has S pistons in his 2,2 E motor. 9,8 to 1 CR. No problems so far with the crap they sell for gas in CA. It is a sweet running motor.

He also has Webers. You will need to do mods to your Zeniths to gain any power from any other improvements you make.

[dpetteng]

So you can slot in 2.2S pistons and barrels with a "e" cam?

Is there much you can do with Zeniths? Obviously not as many options as webers but I really want to keep the originality of the engine and not swap out the carbs. That's really why I was thinking of "e" barrels and pistons as I am not sure I can make the Zeniths gain the benefits of "s" components?

[Trackrash]

Originally Posted by dpetteng

So you can slot in 2.2S pistons and barrels with a "e" cam?

Is there much you can do with Zeniths? Obviously not as many options as webers but I really want to keep the originality of the engine and not swap out the carbs. That's really why I was thinking of "e" barrels and pistons as I am not sure I can make the Zeniths gain the benefits of "s" components?

No problem with S pistons and E cams. The S cams have more lift and duration than the E cams.

I think with just the increase in CR and change to E cams the Zeniths can be made to work. In your case, you would need to go to larger venturis, probably 30mm would work. Then getting the jetting right. There are a couple of threads on building up Zeniths here on Pelican.

FWIW, I found the the Zeniths were better than the Webers on my stock 2,2T. Once I went to a 2,5 with 90mm P&Cs I could never get them to work right. If you are not increasing the displacement much, you should be fine with the Zeniths.

There are those who claim to have Zeniths working on 3,0 motors, I have read.

[dpetteng]

Great, any idea where I can get bigger venturis for the Zenith's? Can't seem to find any.

[bgyglfr]

You can get your venturies machined to spec. It shouldn't take much since you are just moving up one cam size. I think others have found them from performance oriented. Some will even argue that zeniths are superior to webers once you get them set up correctly.

[speedo]

Not to beat a dead horse...if you are going to open the case, swapping the cranks and rods is easy. Keep the same P and Cs and cams. Keep the Zeniths. Stock chokes are 27s (I think) and you can find 28.5s. Engine and carbs look factory, yet you will have 175 hp vs 140 hp. Or, you can buy all the other stuff to improve performance...P and Cs, cams etc $$ and still not have a stock engine. KISS is how I think of projects...what is wanted/needed/necessary.

Just say'in.

Speedo

[tharbert]

A couple points...

Mag cases have their own challenges once you crack them open. Be prepared for a significant machine shop bill: case halves decked and align bored, spigots leveled, time serted head and select internal studs and the while-you're-in-there stuff like oil bypass mod and piston squirters. Mag cases tend to warp when taken apart and reassembly without the machine work may become problematic: stuff simply won't line up. Do a quick search about mag cases and head studs.

There is another conversation about P/C upgrades running close to this thread talking about JE pistons and cast cylinders. It's possible but not recommended mainly because of the difference in expansion coefficients between aluminum pistons and iron cylinders. It's something about which you certainly need to do your homework. It may be better to shop around for a full set of P/C's. There's a reason why they moved away from cast cylinders: they don't dissipate heat as well as the newer options. Heat is not a friend of these old Mag cases.